Subtract.
Answer: There are many ways to solve this problem. Let's see two ways we can solve it. Place Value We can think in terms of hundredths: $\begin{aligned} &\phantom{=}78.43 -6.3\\\\ &=78.43 - 6.30\\\\ &=7{,}843\text{ hundredths} - 630\text{ hundredths}\\\\ &=7{,}213\text{ hundredths}\\\\ &=72.13 \end{aligned}$ Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths Hundredths ${7}$ ${8}$ $.$ ${4}$ $3$ $6$ $.$ ${3}$ $0$ Now, let's subtract each place value column. Tens Ones $.$ Tenths Hundredths ${7}$ ${8}$ $.$ ${4}$ ${3}$ $-$ $6$ $.$ ${3}$ $0$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $7$ $2$ $.$ $1$ $3$ $72.13 = 78.43 - 6.3$